Fault tolerant intersecting beam display panel

ABSTRACT

A two dimensional display panel produces a time variable image composed of light emitting pixels. The pixels are generated by a light emitting phosphor distributed within the panel, the pixels radiate light in response to being excited by charging and triggering energy beams. The energy beams are relatively invisible and may be generated by lasers or solid state diode energy sources. Wave guides within the panel direct the energy beams to the pixels. The wave guides may be composed of fiber optic threads and the display panel comprised of a fabric of woven fiber optic threads wherein pixels are produced at intersections of the woven fiber optic threads. The brightness of the pixels are controlled by regulating the duty cycle of a column driver relative to the duty cycle of a row driver. The display energy beams are driven to facilitate interface with a pen-like pointing device. In one embodiment the pen receives relatively invisible energy beams and in another embodiment the pen receives visible pixel light. In another embodiment, the invention has redundant energy beam sources and driving circuitry in order improve display system reliability.

REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No.09/301,470 filed Apr. 28, 1999 entitled Pixel Brightness Control for andIntersecting Beam Phosphorous Display which is a continuation-in part ofU.S. patent application Ser. No. 08/872,262 filed Jun. 10, 1997 now U.S.Pat. No. 6,031,511.

FIELD OF THE INVENTION

The present invention pertains to a system for producing images, andmore particularly, to a display system having redundant components.

BACKGROUND OF THE INVENTION

Television receivers and other display systems use a cathode ray tubehaving a fluorescent coating deposited on a slightly curved screeninside the tube. In a black and white tube an electron gun directs abeam of electrons toward the screen with the electron beam being scannedover the surface of the screen by vertical and horizontal deflectionsystems. A control grid varies the amount of current in the beam to varythe brightness of different areas on the screen. In a color tube a trioof beams are each intensity controlled and each beam is directed towardone of three colors of phosphor on the screen. However, in both blackand white and in color television the image can be viewed only from thefront of the screen, which is opposite from the side of the screencontaining the phosphor. Further, the electron gun requires that acathode ray tube display system be thick. And still further, the displayis constructed of a rigid glass to facilitate direction of the electronbeam upon the phosphor.

More recent flat panel displays have significantly reduced the thicknessof display systems. Liquid Crystal Display (LCD) systems requireindividually electrically addressable pixels on the display surfacewhich are switched between transparent and opaque states. The pixelsgate light generated typically from an electroluminescence light panelin order to generate the display. Such displays require complexcircuitry to activate each pixel, and are visible typically from theside opposite to the electroluminescence panel.

U.S. Pat. No. 4,870,485 to Downing; Elizabeth A., et. al., Sep. 26,1989, entitled: THREE DIMENSIONAL IMAGE GENERATING APPARATUS HAVING APHOSPHOR CHAMBER, hereby incorporated by reference, describes a threedimensional image generating apparatus having a three dimensional imageinside an image chamber. Such a system has been publicly demonstrated.An imaging phosphor distributed through the image chamber is excited bya pair of intersecting laser beams which cause the phosphor to emitvisible light and form an image as the intersecting beams move throughthe image chamber. The imaging phosphor is a rapidly-discharging, highconversion efficiency, electron trapping type which stores energy from acharging energy beam for a very short time, such as a few microseconds.The imaging phosphor releases photons of visible light when energy froma triggering energy beam reaches phosphor containing energy from thecharging beam. This triggering results in radiation of visible lightfrom each point where the charging energy beam crosses the triggeringenergy beam. A first scanning system directs the charging energy beam toscan through a space in the image chamber and a second scanning systemdirects the triggering energy beam to scan through space in the imagechamber. These two energy beams intersect at a series of points in spaceto produce a three dimensional image inside the image chamber. Theenergy beams are provided by a pair of lasers with one beam in theinfrared region and the other in the blue, green, or ultraviolet portionof the spectrum. However, an electromechanical mirror based beamsteering mechanism makes the display bulky, subject to vibration of thedisplay and the glass cube is rigid.

Thus, what is needed is a thin flexible display panel having multi-colorlight generating pixels which may be viewed from either side of thepanel and requires no moving parts to generate the display. Furthermore,what is need is a method and apparatus for controlling the brightness ofpixels comprised within such a display.

Pen-link pointing devices are used in many applications to facilitate auser's interface with a computer via the computer display and arecurrently widely used in hand held personal computers (HPC). Otherapplications use CRT displays for such an interface. Most pen pointingdevices require a means separate from the display to determine thelocation of the pen or other pointing device relative to the display. Inmost HPCs, the separate means takes the embodiment of a touch sensitivefilm placed over the display.

These films add cost to the product and provide an additionalopportunity for failure of the device. Flexible LCDs are being producefor additional display applications and further complicates the use of apointing device in conjunction with the display because touch sensitivefilm tends to falsely respond to flexing of the display. Furthermore,most current displays, including LCDs and CRTs are fragile and require aclear protective layer, such as a resilient plastic or glass be placedbetween the display surface and a pen-like pointing device in order toprotect the display from damage by the pen-like pointing device. Thisadditional protective layer separates the tip of the pointing devicefrom the display increasing a parallax affect from the perspective ofthe user. Thus, what is needed is a display and a pen-like pointingdevice that can be used without additional locating means such as atouch sensitive film, and that reduces parallax when used.

There are many display applications where fault tolerance and highreliability are essential. Such applications include medical, military,aircraft and spacecraft applications where a failure of a display mayprove critical or even fatal. The reliability of many systems isimproved by adding redundancy, that is duplicating active circuitrywherein redundant circuitry continues operating in event of failure.Redundant display technology is exceedingly difficult to realize inordinary CRT and LCD applications because of the characteristics of thedisplay technology. Thus, what is needed is a display system havingredundant active components capable of continuing operation of thedisplay system in the event of failure of active components of thesystem.

SUMMARY OF THE INVENTION

A display apparatus comprises a panel having a display surfacesurrounded by an edge and an imaging phosphor therein. A first sourcefor radiating a first energy beam enters through a first portion of theedge, a second source for radiating a second energy beam enters througha second portion of the edge, and a third source for radiating a thirdenergy beam enters through a third portion of the edge. A first pixel ofvisible light energy is released by the imaging phosphor at anintersection of the first and third energy beams, and a second pixel ofvisible light energy is released by the imaging phosphor at anintersection of the second and the third energy beams, the first andsecond pixels of visible light having a substantially constant locationon the display surface. Pixel brightness may be varied by varying thetiming of the energy beams.

It is an object of this invention to provide a method for driving anintersecting beam display comprising the steps of sequentially enablingradiation of each of a plurality of substantially non-intersectingenergy beams from a first source, and thereafter sequentially enablingradiation of each of a plurality of substantially non-intersectingenergy beams from a second source wherein energy beams from the firstsource intersect with energy beams from the second source.

It is an object of this invention to provide a pointing device forindicating a location on an intersecting beam display radiated by amultiplicity of beams having first and second wavelengths to producepixels of light having at least a third wavelength comprising a firstdetermining means for determining reception of radiation at the firstwavelength, and a second determining means for determining reception ofradiation of the second wavelength.

It is an object of this invention to provide a method of driving anintersecting beam display comprising the steps of: radiating a firstenergy beam into an intersection; radiating a redundant energy beam intothe intersection; and radiating a third energy beam into theintersection, wherein a first pixel of visible light occurs at anintersection of the first, redundant and third energy beams and thefirst pixel of visible light occurs independent of a failure of eitherthe first or redundant energy beams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a display apparatus having a display panel excited bysources radiating energy beams. FIG. 1 also shows a display apparatushaving redundant switching means, redundant row sources, and redundantcolumn sources.

FIG. 2 shows a display apparatus having a panel composed of orthogonallayers of parallel wave guides having reflectors at an end and animaging phosphor layer interposed between.

FIG. 3 shows an intersection of two wave guides of FIG. 2 and theimaging phosphor there between.

FIG. 4 shows a panel of display fabric having a plurality of parallelfiber optic threads woven orthogonal to another plurality of parallelfiber optic threads, wherein pixels of light are generated by imagingphosphor at intersections of the threads.

FIG. 5 shows a perspective view of the display fabric panel of FIG. 4.

FIG. 6 shows a more detailed block diagram of functions included in adisplay generator and a switching means operating in accordance with thepresent invention.

FIG. 7 shows a timing diagram of energy beams driven by the switchingmeans for creating a matrix of four pixels of varying brightness.

FIG. 8 shows an alternate timing diagram of energy beams driven by theswitching means for controlling brightness of two pixels in a pixelmatrix.

FIG. 9 shows a perspective view of the intersecting beam phosphorousdisplay with a pen-like pointing device.

FIG. 10 shows a block diagram of the intersecting beam phosphorousdisplay with the pen-like pointing device.

FIG. 11 shows a timing diagram of row and column energy beam radiationas well as pixel illumination in accordance with the present invention.

FIG. 12 shows a block diagram of the fault tolerant display systemoperation in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

This is a continuation-in-part of U.S. patent application Ser. No.09/301,470 filed Apr. 28, 1999 entitled Pixel Brightness Control for andIntersecting Beam Phosphorous Display which is a continuation-in-part ofU.S. patent application Ser. No. 08/872,262 filed Jun. 10, 1997, bothare hereby incorporated by reference.

FIG. 1 shows a display apparatus having a display panel excited bysources radiating energy beams. The display panel 10 has an edge 12surrounding it on all sides. The display panel is preferablysubstantially transparent to visible light and has imaging phosphordistributed therein. A first source 20 radiates a first energy beam 22into a first portion of edge 12. A second source 30, preferably having awavelength substantially similar to that of source 20, emits a secondenergy beam 32 into a second portion of edge 12. A third source 40,preferably having a different wavelength from sources 20 and 30,radiates a third energy beam 42 into a third portion of edge 12.

Sources 20 and 30 may represent either triggering or charging energybeams and source 40 may represent either a charging or triggering energybeam respectively, such that the imaging phosphor releases visible lightenergy when energy from a triggering energy beam reaches phosphorcontaining energy from a charging energy beam.

A first pixel of visible light energy 52 is released by the imagingphosphor at intersection of the first energy beam 22 and the thirdenergy beam 42, and a second pixel of visible light energy 53 isreleased by the imaging phosphor at intersection of the second energybeam 32 and the third energy beam 42. The first and second pixels ofvisible light have a substantially constant location on the displaysurface of panel 10. Numerous additional pixels 54 may be added byadding additional sources including sources 55 and 56. Sources 20, 30,40, 55 and 56 may be realized by lasers or solid state diodes emittingenergy beams at appropriate charging and triggering wavelengths.

A switching means 60 is coupled to at least the first, second and thirdsources, 20, 30 and 40. The switching means is responsive to a displaygenerator 62 which generates a display signal for selectively activatingat least the first and second pixels, 52 and 53. Display generator 62may be any of numerous display generators known in the art includingeither a television receiver or a personal computer. The switching means60 enables the first and third energy beams 22 and 42 in response to thedisplay signal indicating activation of the first pixel 52, and enablesthe second and third energy beams 32 and 42 in response to the displaysignal indicating activation of the second pixel 53. The switching means60 enables the first, second and third energy beams, 22, 32 and 42 inresponse to the display signal indicating activation of the first andsecond pixels 52 and 53. Activation of a energy beam may be either byproviding energizing power to its respective source, or a switching ashutter at the output of the respective source. Numerous additionalpixels 54 may be selectively activated by coupling switching means 60 toadditional sources, such as sources 55 and 56 and enabling therespective energy beams in a corresponding way.

The display apparatus of FIG. 1 has an advantage in that the alignmentof panel 10 relative to sources 20, 30, 40, 55 and 56 is not critical solong as the corresponding energy beams are radiated within panel 10. Thepixel location is defined by the intersection of the energy beams withinthe panel, not necessarily the alignment of the panel relative to thesources. This has the advantage of reducing precision manufacturing ofthe display apparatus. Further, panel 10 can be a relatively thin layerof glass or flexible plastic, and since no electrical wiring connectionis necessary within the panel to activate pixels, the cost of the panelmay be significantly reduced. Since the pixel density and display sizeis determined by the number and placement of the sources, and since thesources may be made from low cost high density solid state diodes, alarge size, high pixel density flat panel display can be made. Sinceeach pixel radiates light out of either surface of the panel, a displayproduced by the display apparatus may be viewed from either side of thepanel.

FIG. 2 shows a display apparatus having a panel composed of orthogonallayers of parallel wave guides having reflectors at an end and animaging phosphor layer interposed between. Panel 100 comprises a firstlayer having a first multiplicity of substantially parallel wave guides70-79, for channeling energy beams 22, 32 and 57, and a second layerhaving a second multiplicity of substantially parallel wave guides forchanneling energy beams 42 and 58. The wave guides limit dispersion ofthe energy beams within the layer with a smooth internally reflectivesurface which enables internal reflection of energy beams thereby alsolimiting dispersion and intersection of energy beams within the layer.The layers of FIG. 2 may be comprised of numerous laminated fiber opticpipes. An imaging phosphor layer 90 interposed between the first layer70-79 and second layer 80-88 has the imaging phosphor distributed therethrough. Sources 20, 30 and 55 are coupled to apertures at one end ofthe wave guides of the first layer 70-79 and reflector 92 is coupled toapertures at the other end of the wave guides 70-79. Sources 40 and 56are coupled to apertures at one end of the wave guides 80-88 of thesecond layer and a reflector 94 is coupled to apertures at the otherend. While the sources 20, 30, 40, 55 and 57 and reflectors 92 and 94are shown a distance from their respective layers for illustrativepurposes, they are preferably attached to apertures at the end of thewave guides of the perspective layers.

In FIG. 2, source 20 radiates and energy beam 22 substantially into waveguide 78, source 30 radiates energy beam 32 substantially into waveguide 71, source 40 radiates energy beam 42 substantially into waveguide 82, source 55 radiates energy beam 57 substantially into waveguide 75, and source 56 radiates energy beam 58 substantially into waveguide 85. The panel of FIG. 2 maintains the advantage that the alignmentof the sources with the panel is not critical because a pixel of lightis formed at an intersection of the energy beams. For example, energybeam 32 could be conducted not only by wave guide 71, but by adjacentwave guides 70 or 72 without interference from adjacent energy beam 57and while further maintaining substantially constant pixel location onthe surface of panel 100. The panel of FIG. 2 has the further advantagein that if the energy beams have a tendency to disperse or spread out asthey travel further from the source, the wave guide will tend to limitthe dispersion to within itself. Thus, a pixel generated farther fromthe source, will have substantially the same size as a pixel generatedclose to the source because the size is substantially determined by thedimensions of the wave guide rather than the dispersion characteristicsof the charging and triggering energy beams.

The panel of FIG. 2 has a further advantage in that the reflector at theend of the wave guide tends to compensate for any attenuation of theenergy beam by the wave guide. The sum of the power of energy beamoriginated from the source plus the power of the energy beam reflectedby the reflector should result in a more constant distribution of powerthrough the wave guide. This will help assure a more even brightness ofpixels across the panel.

Another advantage of the panel of FIG. 2 is that the parallel nature ofthe wave guides reduces the requirement of parallel alignment of energybeams generated by the sources of one layer relative to each other, forexample the parallel alignment of energy beams 22, 32 and 57 relative toeach other, and energy beams 42 and 58 relative to each other necessaryto produce evenly spaced pixels is reduced because the wave guides tendto assure the parallel nature of the energy beams even though therespective sources may not accurately generate parallel energy beams.Furthermore, the orthogonal alignment of energy beams of the two layersis reduced, for example the intersection of wave guides 70-79 with waveguides 80-88 assure an evenly space matrix of pixels without a criticalorthogonal alignment of energy beams 22, 32 and 57 with energy beams 42and 58. This should significantly reduce precision manufacturing of theinvention. Further, wave guides 70-79 and 80-88 may be made of anidentical laminated optic material and rotated 90 degrees at the time ofassembly.

FIG. 3 shows an intersection of two wave guides of FIG. 2 and theimaging phosphor there between. Wave guide 71, which conducts energybeam 32 intersects with wave guide 82 which conducts energy beam 42.Wave guides 71 and 82 may be representative of all wave guides of FIG.2. Wave guides 71 and 82 are shown to have hash marks or a shaded sideon one surface indicating that surface is etched or made unsmooth tofacilitate the energy beam of the wave guide to intersect with energybeams of wave guides of other layers. The remaining surface of the waveguide is smooth to facilitate internal reflection of an energy beamwithin the wave guide. As energy beam 32 it transmitted through theetched surface of wave guide 71, it intersects with portions of energybeam 42 transmitted through the etched surface of wave guide 82. Atintersection 53 of both wave guides, the imaging phosphor layer 90receives radiation from both charging and triggering energy beams andthus illuminates visible light. This produces a pixel having a welldefined location on the surface of panel 100 of FIG. 2 due to theorthogonal relationship of the wave guides.

In alternate embodiments, the phosphor of the imaging phosphor layercould be incorporated into either or both the wave guides layers,thereby eliminating the need for a separate imaging phosphor layer.Furthermore color displays may be made by stacking multiple panels 100and their associated energy beam sources, each panel capable ofgenerating a different color of light. For example three panels, havingred, green and blue pixels respectively, would produce colors commonlyused in television and personal computer applications.

Alternately, individual wave guides could cause generation of pixels ofvarious colors: a first compound would be distributed within one waveguide for generating a first pixel with a first color of visible lightenergy and a second compound distributed within another wave guide forgenerating the second pixel with a second color of visible light energy.For example, each wave guide could have a compound to filter light colorgenerated by the imaging phosphor layer. For example, wave guide 78could be tinted to allow red light to pass, while wave guide 74 could betinted to allow green light to pass and wave guide 71 could be tinted toallow blue light to pass. In such a case, the intervening wave guides70, 72, 73, 75, 76, 77 and 79 could be eliminated, combined or maderedundant to an appropriate adjacent wave guide. In another example,imaging phosphor compounds could be made to generate predominantly onecolor of light and then dispersed through a wave guide. For example, ared imaging phosphor could be distributed in wave guide 78, a greenimaging phosphor distributed in wave guide 74 and a blue imagingphosphor distributed in wave guide 71, this allows both the generationof color pixels and the illumination of imaging phosphor layer 90.Finally the energy beams themselves could be modified to make a commonphosphor generate various colors of light pixels. Thus, red, green andblue pixels may be generated, allowing the display panel to generatecolor displays. The intensity of each pixel may be varied by varying theintensity or duration of either the charging or triggering energy beam,or both.

FIG. 4 shows a panel of display fabric having a plurality of parallelfiber optic threads woven orthogonal to another plurality of parallelfiber optic threads, wherein pixels of light are generated by imagingphosphor at intersections of the threads. Display panel 200 is comprisedof a multiplicity of substantially parallel fiber optic wave guides,including 222, 232 and 257, orientated orthogonal to a secondmultiplicity of substantially parallel fiber optic wave guides,including 242 and 258. Light generating pixels occur at intersections ofthe fiber optic threads, such as pixel 53, resulting from a lightemitting phosphor being charged and triggered by energy beam sources 20and 40 as previously described.

FIG. 5 shows a perspective view of the display fabric panel of FIG. 4.Pixel 53 is generated by and intersection of energy beams of fiber opticwave guides 242 and 222. Wave guide fiber optic thread 242 has a surface245 for facilitating intersection of its energy beam with energy beamsof orthogonal wave guides such as fiber optic wave guide 222. Theremaining surface of fiber optic thread 242 facilitates energy beaminternal reflection. Similarly, wave guide fiber optic thread 222 has asurface 225 for facilitating intersection of its energy beam with energybeams of orthogonal wave guides such as fiber optic wave guide 240. Theremaining surface of fiber optic thread 240 facilitates energy beaminternal reflection Surfaces 245 and 225 may be etched or non-smooth tofacilitate energy the intersection of energy beams at pixels 53 and 54.Light emitted from pixels may be generated by illuminating phosphordeposited at the intersection of threads 222 and 242. Alternately eitheror both fiber optic wave guide threads 222 and 242 may have illuminatingphosphor distributed there through. The intersection forming pixels 53and 54 may be made by a friction fit due to the weaving of flexiblefiber optic threads or by fusing the fiber optic threads together at thepixel intersections. Alternately, if a fusing technique is used, a roundfiber optic thread may be used, as the fuse between the threads willfacilitate the intersection of energy beams of the threads to produce apixel.

Referring back to FIG. 4, display panel 200 may generate color images byadding compounds to wave guide threads. For example, as previouslydescribed, a phosphor radiating a predominant red, green and blue colorcould be added to wave guide fiber optic threads 222, 257 and 232respectively. Alternately the wave guides could be tinted, or thecorresponding energy beam sources could be modified to modulate thecolor of a pixel. Furthermore, reflectors could be added an end of eachwave guide thread to compensate for energy beam attenuation aspreviously described.

The panel of FIG. 4 has the advantage of being composed of thin flexiblefiber optic threads, and thus as a panel, it is thin and flexiblesimilar to a cloth. Since fiber optic threads are thin, the pixeldensity of the panel may be relatively high. And as previouslydescribed, panel 200 may produce color images. Pixels of panel 200 canradiate light from both sides of the panel. Further, as previouslydescribed, energy beam sources 20, 30, 40, 55 and 56 may be solid statediodes, consequently no moving parts are needed to produce an image onpanel 200.

Although the wave guides of FIGS. 2, 3, 4 and 5 show a perpendicularorientation between wave guides to form intersections defining pixels,the orthogonal relationship of the wave guides of the contemplatedinvention is not limited to a perpendicular configuration. Theorthogonal relationship of the wave guides include any non-parallelrelationship or a relationship between the wave guides which form anintersection such that illuminating phosphor may be radiated by chargingand triggering energy beams.

FIG. 6 shows a more detailed block diagram of functions included indisplay generator 62 and switching means 60 of FIG. 1. Display generator62 includes a pixel memory 301 which contains pixel brightness signalshaving numerical values indicative of brightness of pixels to bedisplayed on a display. Switching means 60 acts as a fundamentalcomponent of a pixel brightness control means. Switching means 60includes a row driver 302 for timing the occurrence of energy beams inrows of the display panel, such as energy beams created byaforementioned sources 20 and 30 with timing information from timingmeans 306 to generated pixel brightness indicated by the pixel memory.Switching means 60 includes a column driver 304 for timing theoccurrence of energy beams in columns of the display panel, such asenergy beams created by aforementioned sources 40 and 56 with timinginformation from timing means 306 to generate pixel brightness indicatedby the pixel memory. The timing occurrence of an energy beam may beaccomplished in a number of ways including switching the energy beamsource off and on, activating a shutter associated with the source orsteering an energy beam into and out of the intersection with a beamsteering device. In a preferred embodiment, an energy beam radiating arow of the display panel is radiated for a predetermined time. Duringthat predetermined time all of the column energy beams are radiated tocause pixels within the row to be illuminated. The duration of eachcolumn energy beam is modulated to set the desired brightness of eachpixel of the row. Thereafter, another row energy beam is radiated forthe predetermined time and the column energy beams are radiated to setthe brightness of each pixel of the row. This process continues untilall of the pixels of the display are illuminated, the process thenrepeats, creating the appearance of a continuously variable movingdisplay on the display panel, similar to the image displayed on a CRT ofa computer or television.

FIG. 7 shows a timing diagram of energy beams driven by the switchingmeans for creating a matrix of four pixels of varying brightness. Line320 indicates that the energy beam from aforementioned source 20 isradiating a first row on the display panel from events 360 to 366. Line330 indicates that source 30 is off from events 360 to 366. Line 340indicates that an energy beam from source 40 is radiating a first columnon the display panel from events 360 to 362. During this time, a pixelis formed on the display panel at the intersection of energy beams fromsources 20 and 40. Line 340 further indicates that an energy beam fromsource 40 is off for the duration of the energy beam from source 20. Theenergy beam from source 40 is on for substantially 50% of the time thatthe column energy beam from source 20. Thus the pixel occurring at theintersection of the two beams from sources 20 and 40 will besubstantially half the brightness of the pixel if the beam from source40 was on for the entire duration of the beam from source 20.

Line 356 indicates the beam from aforementioned source 56 is on andradiating a second column on the display panel from events 364 to 366.During this time, a second pixel is formed on the display panel at theintersection of energy beams from sources 20 and 56. Line 356 furtherindicates that an energy beam from source 56 is off from events 360 to364. The energy beam from source 56 is on for substantially 25% of thetime that the column energy beam from source 20. Thus the pixeloccurring at the intersection of the two beams from sources 20 and 56will be substantially one quarter the brightness of the pixel if thebeam from source 56 was on for the entire duration of the beam fromsource 20. Thus, the brightness of the aforementioned pixel from source40 is brighter than said pixel from source 56.

Line 320 further indicates that the energy beam from source 20 is offafter event 366. Line 330 indicates that source 30 is radiating a secondrow on the display panel from events 366 to 372. Line 340 indicates thatan energy beam from source 40 is radiating the first column on thedisplay panel from events 366 to 370. During this time, a third pixel isformed on the display panel at the intersection of energy beams fromsources 30 and 40. Line 340 further indicates that an energy beam fromsource 40 is off for the duration of the energy beam from source 30. Theenergy beam from source 40 is on for substantially 75% of the time thatthe column energy beam from source 30. Thus the pixel occurring at theintersection of the two beams from sources 30 and 40 will besubstantially three fourths the brightness of the pixel if the beam fromsource 40 was on for the entire duration of the beam from source 30.

Line 356 indicates the beam from an energy beam from source 56 is on andradiating the second column on the display panel from events 366 to 368.During this time, a fourth pixel is formed on the display panel at theintersection of energy beams from sources 30 and 56. Line 356 furtherindicates that an energy beam from source 56 is off after event 368. Theenergy beam from source 56 is on for substantially 12.5% of the timethat the column energy beam from source 20. Thus the pixel occurring atthe intersection of the two beams from sources 30 and 56 will besubstantially one eighth the brightness of the pixel if the beam fromsource 56 was on for the entire duration of the beam from source 20.

FIG. 7 shows energy beam timing control for creating on the displaypanel four pixels of differing brightness by the intersection ofconstant intensity energy beams from two column sources and two rowsources. In this embodiment, the energy beams from the row sources areperiodically radiated at predetermined rates while the timing of theduration of energy beams from the column sources are varied in order toset the desired brightness of each pixel. The number of pixels may besubstantially increased by increasing the number of row and/or columnenergy beams, wherein rows are sequentially, or otherwise, radiated withrow energy beams of predetermined duration while variable brightnesspixels of the row are created by variable duration radiation from columnenergy beams. By rapidly repeating timings of the row and column drives,the appearance of a moving image may be created on the display panel.

FIG. 8 shows an alternate timing diagram for controlling brightness oftwo pixels in a pixel matrix. Line 420 indicates that the energy beamfrom aforementioned source 20 is radiating a first row on the displaypanel between events 460 and 476. Line 440 indicates that an energy beamfrom aforementioned source 40 is radiating a first column on the displaypanel between events 460-462, 464-466, 468-470, 472-474. During thesetimes, a pixel is formed on the display panel at the intersection ofenergy beams from sources 20 and 40. The duty cycle of line 440 furtherindicates that the energy beam from source 40 is on for substantially50% of the time that the column energy beam from source 20. Thus thepixel occurring at the intersection of the two beams from sources 20 and40 will be substantially half the brightness of the pixel if the beamfrom source 40 was on for the entire duration of the beam from source20.

The pixel generated by energy beams controlled in accord with lines 420and 440 has a similar brightness to the pixel generated by energy beamsof lines 320 and 340 of FIG. 7, except that the illumination of saidpixel of FIG. 8 is distributed substantially over the entire duration ofthe row energy beam of line 420, while said pixel of FIG. 7 is one forthe first half of the duration of the row energy beam of line 320.

Lines 456A, 456B and 456C show different energy beam duty cycles forcontrolling an energy beam from aforementioned source 45. A pixel isgenerated at the intersection of the row energy beam from source 20 andcolumn energy beam from source 56. The duty cycles are 50%, 75% and 25%respectively. Line 456A is the inverse of line 440 resulting in a pixelat the intersection of energy beams from sources 20 and 56 which is onfor 50% of the time and is off while the pixel of FIG. 8 fromintersection of energy beams from sources 20 and 40 is on and visaversa. This has the advantages of not only spreading the illumination ofthe pixel for the duration of the energy beam from source 20 but alsooperates the pixels in a relatively complementary fashion. Lines 456Band 456C show variations in duty cycle from 75% on to 25% on,respectively, relative to line 456A. The variations in duty cycle varythe duration of occurrence of the energy beam. The corresponding pixelformed at the corresponding intersection would have substantially 75%and 25% brightness.

Thus, FIG. 8 shows an alternate method for controlling the brightness ofpixels formed on the display panel using a variable duty cycle on one ofthe energy beams used to form the pixel. It should be appreciated thatwhile duty cycle variations is described in the intersection of aplurality pixels and a multiplicity of energy beam sources, the methodcan also be used to govern the brightness of any two energy beams forcreating visible light as a result of their intersection.

FIG. 7 and FIG. 8 shows a first source column for radiating a firstenergy beam through a first portion of the edge for a first duration, asecond column source for radiating a second energy beam through a secondportion of the edge for a second duration less than the first duration,and a row source for radiating a third energy beam through a thirdportion of the edge for a third duration inclusive of the first andsecond durations. The methods of FIG. 7 and FIG. 8 have the advantage ofproviding for energy beams of constant intensity and variable duration,thereby avoiding the problem of designing energy beams sources capableof producing variable intensity energy beams to control pixelbrightness. The methods of FIG. 7 and FIG. 8 describe varying pixelbrightness, in the preferred embodiment the pixel brightness is variedin response to pixel brightness signals in the pixel memory. Thebrightness may additionally be varied in a predetermined way tocompensate for bright and dark areas on the display as a result ofmanufacturing and other process variations.

Returning to FIG. 4, as previously described, a multiple color display“fabric” may be made by including a differing color phosphor in at leasttwo wave guide fiber optic threads of the display fabric. In this way amultitude of colors may be produced by a grouping of pixels of differingcolors. It is desirable to keep a common sized wave guide fiber opticthread dimension, or thread thickness. When using the aforementioned rowand column drivers of FIG. 6, the resulting pixel grouping isirregularly shaped in that it length is different from its width. Forexample, a pixel grouping of red, green and blue pixels is formed by theintersection column save guide fiber optic threads of sources 40, 56 and500, respectively and row wave guide fiber optic threads of source 20.In order to make the pixel grouping uniform in shape, that is the lengthand width the same, and in order to make the wave guide fiber opticthreads of the same thickness, the grouping could be expanded to includean equal number of rows and columns. In a red, green blue (RGB) example,a red pixel is formed by the intersection of any row wave guide with acolumn wave guide associated with either sources 40 or 502, a greenpixel is formed by the intersection of any row wave guide with a columnwave guide associated with either sources 56 or 504, and a blue pixel isformed by the intersection of any row wave guide with a column waveguide associated with either sources 500 or 506. A regularly shapedpixel grouping would be made by simultaneously driving sources 20, 55and 30 as one row and 510, 512 and 514 as another row. In this way, fourregularly shaped RGB pixel groupings may be formed from the sourcesidentified in FIG. 8. The first pixel is generated by the intersectionof row sources 20, 55 and 30 and RGB column sources 40, 56 and 500. Thesecond pixel is generated by the intersection of row sources 20, 55 and30 and RGB column sources 502, 504 and 506. The third pixel is generatedby the intersection of row sources 510, 512 and 514 and RGB columnsources 40, 56 and 500. The fourth pixel is generated by theintersection of row sources 510, 512 and 514 and RGB column sources 502,504 and 506. The brightness of pixels of the pixel group may becontrolled using the aforementioned switching means of FIG. 6.

Thus what is provided is a thin flexible display panel havingmulti-color light generating pixels which may be viewed from either sideof the panel and requires no moving parts to generate the display.Furthermore, what is provided is a method and apparatus for controllingthe brightness of pixels comprised within such a display, as well as away to create regularly dimensioned pixel groupings capable of producingmultiple colors with a common sized wave guide.

FIG. 9 shows a perspective view of the intersecting beam phosphorousdisplay with an pen-like pointing device. The display panel 600 isoperationally similar to aforementioned display panels 10, 100 or 200.The display panel is driven by row and column sources 602 and 604 whichinclude aforementioned row sources 20, 55, 30, 510, 512 and 514 and theaforementioned column sources column sources 40, 56, 500, 502, 504 and506. The aforementioned switching means 60 and display generator 62 maybe comprised within block 606. A pen-like pointing device 610 is coupledto block 606 with a cable 612. In an alternate embodiment the interfaceto the pen may be wireless. The pen has a tip which is shown to be insubstantial contact with the display 600 at a location 620 having a rowand column axis of “X” and “Y” respectively. The row and column axis arealso indicative of corresponding row and column energy beams having anintersection substantially at location 620 and the tip of the pen on thedisplay panel.

FIG. 10 shows a block diagram of the intersecting beam phosphorousdisplay with the pen-like pointing device and includes the correspondingitems of FIG. 9. Pen 610 has row and column receivers 632 and 634 forreceiving energy beams from row and column drivers 602 and 604. Locationdetermining means 640 compares the timing of signals received from therow and column receivers with the timing signals generated by timingmeans 306 to determine the location of the pen on the display. Inresponse to the determined location, pixel modifier 642 modifies thecolor and/or brightness of pixels substantially at the determinedlocation resulting in, among other things know in the art, electronicink. This give the user the impression that the pen 610 is enablingwriting on the display 600 in much the same way that a familiar ink penenables writing on paper.

FIG. 11 shows a timing diagram of row and column energy beam radiationas well as pixel illumination in accordance with the present invention.The events of the timing diagram are indicated by lines 700-726. The rowenergy beam radiation timing is indicated by lines 750-756, with the rowindicated as “X” in FIG. 9 and FIG. 10 indicated by line 754. The columnenergy beam timing is indicated by lines 758-764, with the columnindicated as “Y” in FIG. 9 and FIG. 10 indicated by line 762. The timingof the visual illumination of the pixel at intersection 620 of FIG. 9and FIG. 10 is shown by line 764.

During events 700-712 the row energy beams 750-756 are sequentiallyradiated while the column energy beams 758-764 are simultaneouslyradiated. For example, between events 700 and 702, row energy beam 750is radiating while the other row energy beams 752-756 are not radiatingand all column energy beams 758-764 are simultaneously enable andradiating for a variable duration. Then, between intervals 702 and 704row energy beam 752 is next in sequence for radiating while the otherrow energy sources are not radiating and all column energy beams 758-764are simultaneously enabled and radiating for a variable duration. Duringevents 714-726 the column energy beams 758-764 are sequentially radiatedwhile the row energy beams 750-756 are simultaneously radiated. Duringsequential radiation, the energy beams are radiated one at a time for apredetermined time. The energy beams may be radiated in a linearsequence from top to bottom or left to right, or in other non-linearsequences which may have the advantage of reducing any appearance ofsweeping or flicker of the display. During simultaneous radiation, allenergy beams of the row or column are enabled for radiation for avariable duration. As previously described, the duration of theradiation is varied to provide for variable pixel brightness. Variableduration is indicated by the multiple rising and falling lines. Also,during simultaneous radiation, energy beams may be kept off for thevariable duration if no visible light is to be generated by thecorresponding pixels, as indicated by the always “low” state during thesimultaneous radiation mode.

The timing of the visual illumination of the pixel at intersection 620of FIG. 9 and FIG. 10 is shown by line 764. Line 764 indicates that thepixel is radiating visible light of variable brightness between events706 and 708 when energy beam 754 is radiated for the predeterminedduration and energy beam 762 is radiated for the variable duration. Thepixel is also radiating visible light of variable brightness betweenevents 720 and 722 when energy beam 754 is radiating for the variableduration and energy beam 762 is radiating for the predeterminedduration.

Referring back to FIG. 10, the operation of the elements of the blockdiagram are explained with reference to timing diagram of FIG. 11. Therow receiver preferably includes a phototransistor optimized forreceiving energy beams of the wavelength of energy beams from the rowsources and column receiver preferably includes a phototransistoroptimized for receiving energy beams of the wavelength from the columnsources. In one embodiment the optimization includes an optical filterin front of each phototransistor for passing the desired wavelength. Inanother embodiment a single receiver can be electronically tuned toreceive energy beams of either the row or column wavelengths whileeither is correspondingly operating in its sequentially driven mode.

Since the row sources are sequentially driven while the column sourcesare simultaneously driven followed by the column sources beingsequentially driven and the row sources simultaneously driven, thelocation determining mean can determine the location of the pen bymatching the generated and received occurrences of row and columnsequences. In this mode the row and column receptions while either is inthe simultaneous mode are ignored. For example, with the tip of the penat intersection 620, the row receiver receives a signal having a timingsubstantially equal to that of line 754 and the column receiver receivesa signal having a timing substantially equal to that of line 762. Bycomparing the received signal timings with the signals generated by thetiming means, the location determining means can determine the locationof the tip of the pen on the display to be substantially at intersection620 of energy beams 754 and 762. In determining the location, thelocation determining means could further approximate for reception ofmultiple adjacent energy beams by the receivers as well as apredetermined delay between the received and generated signals viasystem calibration.

Since this form of location determining relies on the reception of thesubstantially invisible row and column energy beams, the location of thepen may be advantageously determined independent of the pixelsilluminated on the display. For example, the location of the pen may bedetermined when there are no pixels illuminated on the display, becausethe location is determined by the matching the occurrence of invisiblesequential row and column energy beams. Also, since this embodiment doesnot rely upon visible light for determining location, interference fromvisible light sources can also be reduced.

In an alternate embodiment, row and column receivers 632 and 634 arereplaced by a single visible light receiver (not shown). In thisembodiment, the pen tip at location 620 receives the unique visiblepixel radiation timing of line 766 of FIG. 11. Since the pixel at line766 has a unique visible light timing, the location determining meanscan compare the received signal timing with the signals generated by thetiming means in order to determine the location of the tip of the pen onthe display. In determining the location, the location determining meanscould also approximate for reception of multiple adjacent pixel by thereceiver as well as a predetermined delay between the received andgenerated signals via system calibration.

This alternate embodiment has the advantage of requiring only a singlevisible light receiver and operates in response to illumination ofpixels. In an example of this mode, the display would be illuminated asif it were a white page and the pixel modification in response to thedetermined location of the pen would be displayed as a colored ink.

The invention has the advantage of a method for driving an intersectingbeam phosphorous display which facilitates locating a pen-like pointingdevice on the display. The location is determined by comparing receivedradiated signals with signals generated in order to drive the display,no additional position sensing is necessary, such as a touch sensitivepad or other means to determine the location of the pointing device.Since the display may be thin flexible glass or plastic with an imagingphosphor, and no active components on either side of the displaysurface, the display itself is resilient and needs very littleprotection from damage by the pen. Thus, the geometry of the displayallows for a very close proximity between the displayed pixels and thereceivers in the pen. This advantage significantly reduces parallax whenusing the pointing device. Furthermore, receivers of the pen may besimilarly positioned very near the tip of the pen, further reducingparallax.

Referring back to FIG. 1, FIG. 1 shows a display apparatus havingredundant switching means 780, redundant row sources 782, 784 and 786,and redundant column sources 788 and 790. The operation of the redundantswitching means 780 is substantially identical to the operation ofswitching means 60. Redundant row energy beam sources 782, 784 and 786operate substantially identically to corresponding row energy sources20, 55 and 30, all sources radiating invisible energy beams ofsubstantially the same wavelength or frequency however in an oppositedirections. Thus, energy beams from sources 20 and 782 radiate alongpath 22 but in opposite directions, energy beams from sources 55 and 784radiate along path 57 but in opposite directions and energy beams fromsources 30 and 786 radiate along path 32 but in opposite directions.Similarly, redundant column energy beam sources 788 and 790 operatesubstantially identically to corresponding column energy sources 56 and40, all sources radiating invisible energy beams of substantially thesame wavelength or frequency however in an opposite directions. Thus,energy beams from sources 788 and 56 radiate along path 58 but inopposite directions, and energy beams from sources 790 and 40 radiatealong path 42 but in opposite directions.

The redundant elements of FIG. 1 have the advantage of providing forfault tolerant pixel illumination of all pixels 52, 53 and 54 of thedisplay even if one or several components fail. For example if switchingmeans 60 were to fail, causing all energy beams controlled thereby toalso fail, the energy beams from the redundant switching means andsources 780-790 would radiate the along paths 22, 32, 42, 57 and 58 toenable pixels 52,53 and 54 to illuminate. Similarly, should individualenergy beam sources fail, the corresponding redundant source wouldcontinue to radiate an energy beam along the desired path. A similarfault tolerance occurs at an interface between the energy beam sourceand the display.

Referring back to FIG. 4, FIG. 4 further shows redundant row and columnsources used in conjunction with the multiple wave guide display. Theredundant row sources include sources 782, 784 and 786. The redundantcolumn sources include sources 788 and 790. It should be appreciated rowand column reflectors 92 and 94 of FIG. 2 could also be replace byredundant sources resulting in a benefit similar to the reflectorsincluding a brighter display and more uniform pixel brightness. Also,redundant row and column sources and drivers may be incorporated intothe pen pointing device of FIG. 9 without substantial modification tothe operation of the pointing system.

FIG. 12 shows a block diagram of the fault tolerant display systemoperation in accordance with the present invention. The switching means60, pixel memory 301, row and column drivers 303, timing means 306, anddisplay 600 operate substantially identically to the correspondingelements of FIG. 10. The row and column sources 603 include row andcolumn sources 602 and 604 of FIG. 10. The redundant components includeswitching means 780 having row and column drivers 793 and timing means796 are coupled to redundant row and column sources 798 which includesaforementioned sources 782-790. The switching means and its componentsare substantially identical to and operate in substantialsynchronization with corresponding switching means 60 and its componentsin order to illuminate pixels on the display. Synchronization and faultdetection means 799 operates to synchronize the two switching means 60and 780 so that redundant energy beam radiation occurs in substantialsynchronization. Means 799 further acts to monitor signals produced bythe timing means 306 and 396 and row and column drivers 303 and 793 forsignal indicative of a failure of circuitry therein or the energy beamsources. A signal may be generated in response to self check circuitsdetecting a failure in order that further corrective action may betaken. Further, if a failure causes an energy beam to remain radiatingwhen it is supposed to be off, the source itself, all of thecorresponding row or column sources, the corresponding drivers and/ortiming means may be deactivated and the display continues to operatewith the redundant circuitry. In alternate embodiments, additionalredundant components may be added such as power supplies, pixel memoriesand computer systems used to generate images stored in the pixelmemories.

The fault tolerance characteristics of the present invention have theadvantage of being easily and inexpensively realized, similar redundantsystems are excessively complex and/or expensive to realize in CRT orLCD displays, if at all possible. Further, the display itself is passivehaving no active components or liquid crystal films thereby furtherimproving the reliability of the display system. The combination ofredundant active components driving a passive display panel provides anexceeding reliable color display having in medical, military, aircraftand spacecraft applications where reliability and fault tolerance areessential. Thus what has been provided is a fault tolerant displaysystem having redundant active components and a passive display panel.

I claim:
 1. A display apparatus comprising: a panel having a displaysurface surrounded by an edge, said panel further having an illuminatingmaterial therein: a first source for radiating a first energy beamthrough a first portion of the edge in a first direction along a firstpath; a redundant source for radiating a redundant energy beam throughanother portion of the edge in a direction substantially opposite to thefirst direction and substantially along the first path; a third sourcefor radiating a third energy beam through a third portion of the edge,wherein a first pixel of visible light energy is released by theilluminating material at an intersection of the first, redundant andthird energy beams whereby the first pixel of visible light is releasedindependent of a failure of either the first or redundant energy beam.2. The display apparatus according to claim 1 wherein the first pixel ofvisible light has a substantially constant location on the displaysurface.
 3. The display apparatus according to claim 1 furthercomprising a wave guide having a first end for receiving the firstenergy beam and a second end for receiving the redundant energy beamwherein said wave guide substantially defines the first path andsubstantially directs the first and redundant energy beams along thefirst path.
 4. The display apparatus according to claim 1 wherein thethird energy beam is radiated in a third direction along a third pathand the apparatus further comprises a third redundant source forradiating a third redundant energy beam through a third other portion ofthe edge in a direction substantially opposite to the third directionand substantially along the third path, further wherein the first pixelof visible light energy is released at the intersection of the first,redundant, third and third redundant energy beams further whereby thefirst pixel of visible light is released independent of a failure ofeither said third or said third redundant energy beam.
 5. The displayapparatus according to claim 1 further comprising: a second source forradiating a second energy beam through a second portion of the edge insubstantially the first direction along a second path; a secondredundant source for radiating a second redundant energy beam through asecond other portion of the edge in a second direction substantiallyopposite the first direction and substantially along the second path,wherein a second pixel of visible light energy is released by theilluminating material at a second intersection of the second, secondredundant and third energy beams whereby the second pixel of visiblelight is released independent of a failure of either the second orsecond redundant energy beam.
 6. The display apparatus according toclaim 5 wherein the third energy beam is radiated in a third directionalong a third path and the apparatus further comprises a third redundantsource for radiating a third redundant energy beam through a third otherportion of the edge in a direction substantially opposite the thirddirection and substantially along the third path, further wherein thefirst pixel of visible light energy is released by the imaging phosphorat an intersection of the first, redundant, third and third redundantenergy beams and the second pixel of visible light energy is released atthe second intersection of the second, second redundant, third and thirdredundant energy beams and further whereby the first and second pixelsof visible light are released independent of a failure of either saidthird or said third redundant energy beam.
 7. The display apparatusaccording to claim 6 further comprising: a driver means for controllingradiation of the first, second and third energy beams; and a redundantdriver means for controlling radiation of the redundant, secondredundant and third redundant energy beams wherein said redundant drivermeans is substantially independent of said driver means.
 8. The displayapparatus according to claim 6 further comprising: a timing means forcontrolling timing of radiation of the first, second and third energybeams; a redundant timing means for controlling timing of radiation ofthe redundant, second redundant and third redundant energy beams whereinsaid redundant driver means is substantially independent of said drivermeans; and a synchronization means coupled to said timing means and saidredundant timing means wherein the first and redundant energy beams havesubstantially identical timing, and the second and second redundantenergy beams have substantially identical timing, and the third andthird redundant energy beams have substantially identical timing.
 9. Thedisplay apparatus according to claim 8 wherein said synchronizationmeans further comprises a fault detection means for determining ininequality in timing between said timing means and said redundant timingmeans and for generating a fault detection signal in response thereto.10. A method of driving an intersecting beam display comprising thesteps of: radiating a first energy beam into an intersection; radiatinga redundant energy beam into the intersection; and radiating a thirdenergy beam into the intersection, wherein a first pixel of visiblelight occurs at the intersection and occurs independent of a failure ofeither the first or redundant energy beams and further wherein theintersection includes an illuminating material for converting the energybeams of the first and second wavelengths into light of a visiblewavelength.
 11. The method according to claim 10 wherein the first andredundant energy beams have a substantially common and invisible firstwave length, the third energy beam has a substantially invisible secondwavelength, and the first pixel has a substantially.
 12. The methodaccording to claim 10 wherein said step of radiating the first energybeam includes the step of radiating the first energy beam in a firstdirection along a first path, and said step of radiating the redundantenergy beam includes the step of radiating the redundant energy beam ina direction opposite the first direction and along the first path. 13.The method according to claim 10 further comprising the step ofradiating a second energy beam into a second intersection of the secondand third energy beams, the second intersection having a locationdifferent from a location of the first intersection, wherein a secondpixel of visible light occurs at the second intersection.
 14. The methodaccording to claim 10 further comprising the step of radiating a thirdredundant energy beam into the intersection, further wherein the firstpixel of visible light occurs at the intersection and occurs independentof a failure of either the third or third redundant energy beams.
 15. Amethod of driving an intersecting beam display comprising the steps of:radiating a first energy beam into an intersection; radiating aredundant energy beam into the intersection; and radiating a thirdenergy beam into the intersection, wherein a first pixel of visiblelight occurs at the intersection and occurs independent of a failure ofeither the first or redundant energy beams and further wherein the firstand redundant energy beams have a substantially common and invisiblefirst wave length, the third energy beam has a substantially invisiblesecond wavelength, and the first pixel has a substantially visiblewavelength.
 16. The method according to claim 15 wherein theintersection includes an illuminating material for converting the energybeams of the first and second wavelengths into light of a visiblewavelength.
 17. The method according to claim 15 wherein said step ofradiating the first energy beam includes the step of radiating the firstenergy beam in a first direction along a first path, and said step ofradiating the redundant energy beam includes the step of radiating theredundant energy beam in a direction opposite the first direction andalong the first path.
 18. The method according to claim 15 furthercomprising the step of radiating a second energy beam into a secondintersection of the second and third energy beams, the secondintersection having a location different from a location of the firstintersection, wherein a second pixel of visible light occurs at thesecond intersection.
 19. The method according to claim 15 furthercomprising the step of radiating a third redundant energy beam into theintersection, further wherein the first pixel of visible light occurs atthe intersection and occurs independent of a failure of either the thirdor third redundant energy beams.